Pulmonicola cochleotrema in dugongs from the Andaman Sea, Thailand — morphological and molecular characterization with pathological implications https://doi.org/10.12982/VIS.2026.056
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Abstract
Dugongs (Dugong dugon), the only extant herbivorous marine mammals, are vital to the maintenance of seagrass ecosystems but are currently listed as vulnerable on the IUCN Red List. In Thailand, the Andaman Sea supports the country’s largest dugong population, yet mortality remains a serious concern, with parasites increasingly recognized as important natural threats. Respiratory trematodes such as Pulmonicola cochleotrema are known pathogens of sirenians, but their status in Thai waters has not been documented. Between January 2019 and May 2025, 166 stranded dugongs were systematically necropsied by veterinarians of the Department of Marine and Coastal Resources. Carcasses were examined for respiratory trematodes, and detailed records of parasite counts, anatomic distribution, and gross lesions were compiled. Representative adult worms were collected for morphological study, histopathology, and DNA-based phylogenetic analysis. P. cochleotrema infection was confirmed in 10 animals (6.02 %), comprising 40 % sub-adults, 40 % adults, and 20 % dependent calves, with no sex-related difference. Parasites were detected throughout the respiratory tract—nares (1/10), nasal cavity (2/10), trachea (3/10), bronchi (1/10), and pulmonary parenchyma (1/10). Gross lesions ranged from mild to moderate mucosal congestion and hemorrhage to severe verminous bronchopneumonia with suppurative exudation. Histopathology revealed severe chronic eosinophilic tracheobronchitis and bronchopneumonia. Morphologically, adult worms were ovoid and dorsoventrally flattened with a muscular fringe; molecular analysis confirmed their identity as P. cochleotrema. This study provides the first comprehensive evidence of P. cochleotrema infection in Thai dugongs, defining its occurrence, morphology, molecular characteristics, and pathological impact. These baseline data enhance understanding of parasite–host interactions and support future health management and conservation strategies for this threatened marine mammal
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